Wanted: Macbook Pro 15"

I would like to buy a macbook pro 15" late 08 or mid09 unibody version. i have £950 or can trade for a dell studio xps 16 which is fnew and unused. it is a present but i dont want it and want a macbook pro 15" instead.
I am trying to find a macboook pro 15" which has 4gb but i might consider 2gb depends or the price.